The present invention relates to a method and a system for controlling a stand-by braking torque applied to an automotive vehicle under a condition of approaching or following an obstacle preceding the vehicle. The term xe2x80x9cobstaclexe2x80x9d is used herein to mean a stationary or moving object within the path of the vehicle, for example, vehicles, pedestrians, etc.
JP-A 7-144588 discloses a system whereby traveling speed and deceleration of an obstacle preceding a host vehicle are determined using a Doppler sensor and a vehicle speed sensor, which are on the vehicle, and a desired distance from the obstacle is determined. In this system, a vehicle operator is warned and an automatic braking action is initiated if the distance from the obstacle becomes less than the desired distance.
Other systems have been proposed that are intended to initiate braking action before a vehicle operator initiates braking action. JP-A 8-80822 discloses a system whereby, when the time rate of change of an accelerator angle upon operator releasing the accelerator pedal exceeds a predetermined level, a brake actuator is activated to partially activate a braking system before the foot of the operator is stepped on the brake pedal.
The action required under such proposed procedures, whether to apply stand-by braking torque, is intrusive. Inaccurate indications that the vehicle operator braking action is imminent, requiring application of stand-by braking torque prior to the operator braking action, can reduce vehicle operator satisfaction and can reduce confidence in the control system. Such inaccurate indications should therefore be minimized.
Many automatic vehicle control approaches are subject to frequent inaccurate indication conditions. Such inaccurate indication conditions may result from modeling error. For example, mathematical models determining conditions under which stand-by braking torque is applied may be oversimplified, relying on broad assumptions about vehicle behavior and operator requirements. Use of such proposed models has resulted in limited commercial acceptance of automatic vehicle control.
An object of the present invention is to provide a method and a system for controlling stand-by braking torque applied to an automotive vehicle in a manner not to reduce vehicle operator satisfaction in the system.
The present invention provides a method for controlling a stand-by braking torque applied to an automotive vehicle under a condition of approaching or following an obstacle preceding the vehicle, the automotive vehicle having a powering system for applying a driving torque to the vehicle in response to an operator power demand, the method comprising:
determining a variable indicative of dynamic situation of the vehicle;
sampling the determined values of the dynamic situation indicative variable immediately before an operator braking action to reduce the speed of the vehicle is imminent;
using the sampled values of the dynamic situation indicative variable as a basis to establish a parameter; and
using the established parameter as a basis to determine a target value of stand-by braking torque, which is to be applied when the operator braking action to reduce the speed of the vehicle is imminent.